


A Good Fit

by tuesday



Category: Marvel Cinematic Universe
Genre: Alternate Universe - Canon Divergence, Canon-Typical Violence, Coffee, Explicit Sexual Content, Fix-It of Sorts, Symbiotic Relationship, Venom!Tony Stark, Venom-Typical Cannibalism
Language: English
Status: Completed
Published: 2019-08-19
Updated: 2019-08-19
Packaged: 2020-09-06 12:09:41
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 4,302
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20291227
Author URL: https://archiveofourown.org/users/tuesday/pseuds/tuesday
Summary: When Tony bonded with an alien entity as a dumb college student who didn't know better, he couldn't have expected this.  The eating chocolate (and sometimes people) thing?  Yes.  An inability to have privacy unless he'd offloaded his friendly, needy symbiote into his pet rabbit that existed solely for the purpose of letting Tony get drunk and/or laid?  Fine.  Having an arc reactor and shrapnel shoved out of his chest when he got home from the one business trip he hadn't bothered to bring Venom on (and subsequently regretted)?  Why not.But this was untenable.





	1. Chapter 1

**Author's Note:**

  * For [pleurer](https://archiveofourown.org/users/pleurer/gifts).

> This got away from me a little bit. It was supposed to be just porn. I think we have all learned a very important lesson here, which is that I am easily caught by canon divergence.
> 
> Venom in this is movie Venom. I'm using he pronouns as in Venom 2018 (film). How and when he got to Earth diverges majorly from canon, but isn't really gone into.

When Tony bonded with an alien entity as a dumb college student who didn't know better, he couldn't have expected this. The eating chocolate (and sometimes people) thing? Yes. An inability to have privacy unless he'd offloaded his friendly, needy symbiote into his pet rabbit that existed solely for the purpose of letting Tony get drunk and/or laid? Fine. Having an arc reactor and shrapnel shoved out of his chest when he got home from the one business trip he hadn't bothered to bring Venom on (and subsequently regretted)? Why not.

But this was untenable.

_That one. You should mate that one,_ Venom said.

_That is a high school student,_ Tony sent back, appalled.

_He caught a SUV with his bare hands,_ Venom said admiringly.

_No,_ Tony said.

But that didn't stop Tony from making the kid a suit. He had skills. He deserved an upgrade.

—

_You could always use me,_ Venom offered when Tony was trying to figure out who to bring with him to bring Cap in.

_Every time I use you instead of the suit, you eat someone,_ Tony pointed out.

_And they all deserved eating,_ Venom said.

_You ate **Obie**,_ Tony said.

_And he deserved it._

Tony couldn't really argue with that.

_You should invite the Spider-Man._

Tony both did and didn't want to. _High schooler,_ Tony repeated, though it wasn't like Venom understood that any more this time than he had the last. Tony could explain human concepts until he was blue in the face, and Venom would still think they were stupid. _We don't come fully grown like you do._

_You should._

Tony sighed. Thirty years, and for some reason he kept trying. _We don't._

—

"You have my permission to eat him," Tony said when the video was done playing.

_We are not eating your friend's friend,_ Venom said.

"He killed _my mom_," Tony said.

_You'll get mad at me later. Or yourself. You don't mean it._

So Tony tried to kill Barnes himself. It didn't really work out.

—

Venom wanted to go for a hug when they dropped Peter off at home. Tony said he was getting the car door. Venom practically thrummed with contentment when Peter took the hug anyway.

—

Peter turned out to be kind of a disaster. Tony adored him and was frustrated by him in equal measure.

_You're worried,_ Venom said. _We could always spawn—_

"No. We are not making another mini you after the last time. _Especially_ not to give to someone else."

_Or we could bond—_ Venom tried.

"Absolutely not."

Venom sulked. Tony set to work updating the suit, because he couldn't even pretend to himself that he wasn't going to give it back.

—

Peter had just started his junior year when he took advantage of the open lab access Tony had given him and, already talking a mile a minute, went on a diatribe about how what happened to his suit wasn't his fault, and anyway, it was only a little tear, you could barely see it, so don't mind him as he repaired it, really, no help or questions necessary. He stopped. He actually looked at Tony. He said, "That's a new suit."

"Yep," Tony said awkwardly as Venom pulled his tendrils back into Tony's body. "Very new. Definitely didn't have this before."

"That's not actually a suit," Peter said slowly.

"It's sort of a suit," Tony said. "Incorporating the nanotech is a work in progress."

Peter came over. He poked at a bit of inky blackness that remained outside of Tony's skin. "That's organic."

"Haven't made much progress yet," Tony said.

"Mr. Stark." Peter looked very confused. "Why can your arm turn black and split into five extra appendages?"

"Okay, it's not new." Tony sighed. He trusted Peter. "Venom, say hi."

Venom popped a head out beside Tony's. The first time he'd done it with Pepper, she'd screamed. The first time he'd done it with Happy, Happy had punched him in his teeth and cut open his hand as he demanded for Venom to let Tony go. Peter? Peter's eyes widened as he said, "That's so cool!"

_We are keeping him,_ Venom said.

_Let's not get ahead of ourselves,_ Tony said.

"Can I touch you?" Peter asked, and Tony was reminded of Rhodey and college, of the way Rhodey had wanted to rub Venom's head like he was a stray dog Tony had picked up.

"_Yes_," Venom said. He preened as Peter stroked a fingertip across his forehead.

"Are you a genetic experiment or an alien?" Peter wondered.

"Both," Tony said.

Honestly, not the worst way Peter could have found out.

—

After that, Tony accepted there was no getting rid of Peter. If he could accept that Tony had spent practically his entire adult bonded to an alien life form, he could probably accept anything. Peter wasn't going anywhere.

Tony found himself regretting that the next year when Peter snuck aboard a spaceship headed toward another planet for a final confrontation Tony had spent the last six years preparing for.

—

They tried and failed to get the gauntlet off of Thanos's arm.

_Tony. Bad guy,_ Venom said insistently.

"Yeah. Bad guy," Tony agreed, resigned to what came next. "Peter, let go."

They started with the arm, because Mantis had hold of the guy's head. It was certainly one way to get the gauntlet off.

"I want to know what happened to Gamora," Quill said insistently before Venom could progress further than snapping Thano's arm off at the elbow with his teeth.

"No, you don't," Nebula said softly.

"I've got the glove," Peter said, picking up the arm and hopping backwards.

Thanos came out of his trance with a roar of pain. He tried attacking. Venom went for the head this time.

"Please tell me someone here has mouthwash," Tony said when it was all over.

"No time for personal hygiene," Strange said. He already had a portal open. "There's an alien army attacking Earth."

—

"You ate that guy," Peter said when they were back in New York. Tony had tried to send him home, but he'd asked if he could stick around the lab for a while. Tony hadn't had the heart to tell him no. Instead, he'd gotten both suits off of Peter and was busy repairing them.

"It was him or half the universe," Tony said defensively.

"But you don't normally eat people, right?" Peter asked. He had the mask from the Mark I in front of him and pulled out a cracked lens.

"Not normally," Tony agreed. For his part, he was seriously considering trashing the first suit and starting over. This level of alien blood was never going to come out of the fabric. Tony would know. "Venom can get what he needs from other sources."

"Is that why you drink those weird smoothies?" 

"Those are for me," Tony said. He put down the tool in his hand next to the wrecked suit. At least every place something had gone through the Iron Spider, the nanotech had been able to repair when Tony hooked the casing up to a power source and more material. "The gourmet chocolate addiction is all Venom."

"_He likes it, too_," Venom said.

"Huh." Peter's affect was muted. He ran his fingers along the edge of the cracked lens. He hadn't looked at Tony for the last ten minutes.

"Okay, come on, out with it. What's up?" Tony turned fully toward Peter. "Is it the eating people thing, space, that battle? There's a lot of ground to cover, and the only person I have a psychic bond with is Venom."

"I killed people," Peter said quietly. "I activated Instant Kill Mode, and they just—it—"

"I could tell you that it was them or you," Tony said, putting a hand on Peter's shoulder. "And I could tell you that it was an invasion, and they'd already killed before. I could tell you that it was the suit working under directives _I_ gave it. I could tell you that you made the right decision and I'd choose you over a thousand, a hundred thousand people trying to kill you." Tony squeezed gently. "But I can tell you now that whatever the rationalization, it's cold comfort, and you're going to have a rough time of it."

Peter leaned forward until his forehead rested against Tony's chest. "I never wanted to hurt anyone."

Tony put his arms around Peter. "I know, kid. I know."

—

It seemed like hardly any time passed at all before Tony turned around and there Peter was, no longer a high school student, but still in Tony's life, building things and wanting to talk about his patrols and getting involved in all sorts of shenanigans. He hadn't gotten that much taller, but his shoulders were broader. He moved more confidently. He was three-quarters of the way through college and almost old enough to drink. He had an ass someone (Tony) could bounce a quarter off of, showcased by where he was bent over in the lab retying his shoelaces, denim pulled tight across it. He could still catch a semi with his bare hands.

He'd … kind of grown up hot.

"Oh, no," Tony said.

_Are you ready yet?_ Venom asked curiously.

"I will never be ready for this," Tony said, feeling like he needed to sit down even though he was already sitting.

"Are we not getting dinner after all?" Peter asked as he straightened.

Tony stood. "We're getting dinner. Just let me get my coat."

_You should mate him,_ Venom said with all the assuredness he'd had the first time.

Tony didn't have an immediate counterargument at hand. He was in so much trouble.

—


	2. Chapter 2

Peter had asked Tony once why he didn't date anymore. 

"I have an incredibly codependent relationship with a permanent alien house guest," Tony answered, not minding the personal question considering Peter was going through a superheroism related break up at the time. "Even if I found someone willing to put up with the rest of my life, that's probably going to be a bridge too far, and it's just not worth the security risk."

"Oh, so you and Venom—" Peter trailed off, probably not sure how to phrase that.

"Oh. Oh, no. Not like that. It's—" Tony didn't really know how to describe it. "We have a unique relationship, but he doesn't fill the romantic square on my personal bingo card." Tony wasn't about to explain his sex life to a teenager, even if Peter was a college student at the time. "I used to have this pet rabbit, Mr. Flopsy, for when I wanted to go on casual dates, but after Afghanistan—" Tony kept his voice steady, kept moving right past that memory. "—Venom wanted to go everywhere with me, and I've never regretted obliging him."

"So the key is finding someone who already knows all your secrets," Peter said thoughtfully.

"If that was the only prerequisite, I'd be dating Nick Fury," Tony said. He grinned at Peter's crestfallen expression. "Chin up, kid. You'll find the right person someday."

—

_You could be the right person,_ Venom encouraged Tony as they dwelled on that particular memory during dinner.

_Does that really sound like a good idea to you? No, don't answer that. Of course that sounds like a good idea to you, because you continue to have no concept of human norms._ Tony poked at his steak and wished he could box it up to take home and let Venom eat it instead.

"You're making that face again," Peter said as he speared a piece of asparagus. "Like you're arguing with Venom in your head."

"We're not arguing," Tony said. "We're just having a minor disagreement."

"Can I at least get in on half of the conversation? Because I'm feeling kind of like I'm eating alone here."

This. This right here was part of why Tony would make an awful boyfriend.

_He suggested a compromise,_ Venom said. _What a good help-meet he would make._

"Your ideas are bad and you should feel bad," Tony said aloud.

Peter beamed at Tony.

Tony didn't know what to do with the knowledge he wanted to kiss the smile off of Peter.

_Kiss him,_ Venom said.

"You are the least helpful, and I hate you," Tony said.

The server, who'd just stopped at the table, shot Tony a scandalized look, but all she said was, "Does anyone need a refill?"

"Can I get more water?" Peter asked.

Tony had been planning to leave a large tip as a matter of course, but now he was probably going to need to leave a bigger one.

—

After dinner, Peter turned down a ride. Tony got in his car and headed for home.

"So. I'm kind of fucked," Tony admitted.

_Yes. Get fucked,_ Venom said, not an imprecation for once. _Or fuck him. It would make you both happy._

"Maybe he's already dating someone," Tony said. "What if he's already dating someone?"

_We could eat them,_ Venom said like that was a reasonable solution.

"Venom, no."

_We could … scare them a little?_ Venom got an obstinate feeling to him. _Whoever they are, they don't deserve him._

Fuck it. Tony had always been a pull the band-aid off kind of guy. "F.R.I.D.A.Y., call Peter."

Peter picked up right away. "Is everything okay? Did something happen?"

"Everything's fine," Tony said. "I was just wondering if you wanted to get coffee sometime. The two of us. Together." Fuck. He was so bad at this. He hadn't picked anyone up in years. He hadn't asked anyone out for real since that one disastrous attempt with Pepper. "As a date."

"Are you serious?" Peter asked. "Is this—is this a coded message? Does someone have a gun to your head right now? I'm not on the train yet. I can come help."

"If they did, Venom would eat them," Tony said. The steering wheel creaked under his grip. "You can say no."

Peter was quiet for a nerve-wracking twenty-eight seconds. Tony counted them. When Peter spoke, all he said was, "Yes. I'd like that."

"Good," Tony said.

"Good," Peter said.

"We'll work out the details later. Catch your train." Tony's heart was pounding despite doing nothing more demanding than sitting in traffic. "I'll call you."

"Talk to you later," Peter said like this was any other phone call between them. He disconnected.

Tony slumped in his seat. "Why did you let me do that?"

_It was a good decision,_ Venom said.

"This from the guy who once ate garbage from a dumpster."

_You were there, too,_ Venom said.

"Protesting vigorously."

_And we weren't the only one._

"The raccoon doing it first isn't an excuse."

_He's not a raccoon._

"He eats out of the garbage!"

_Do you think we're a raccoon?_

Tony sighed. He was smiling. "Thank you for trying to distract me."

_It will work out. You'll see._

—

They went for coffee that weekend. It was weird how not weird it was. They got the coffee to go and walked and talked. Peter talked about his patrols and personal projects and movies he'd seen with friends. Tony talked about the more interesting parts of his work and personal projects and how Venom had broken another blender.

_It was already broken,_ Venom groused.

"Most sound that way normally," Tony said. "Peter, tell him for me, because over three decades has not gotten it through his head: blenders are loud."

"Yours are surprisingly quiet," Peter said.

"Yes, because I designed them that way after a series of temper tantrums by someone who should know better."

_I am much more useful than any blender,_ Venom declared.

"When I let you do it, the smoothies turn out chunky. Smoothies should be smooth," Tony insisted.

Peter smiled and hid it behind his travel mug.

"What?" Tony asked.

"Nothing. It's just—it's nice that you're not hiding your conversations when you're with me." Peter took a sip of his coffee. "I always like seeing you interact."

_He likes me,_ Venom said smugly.

"Don't get a big head about it." He grabbed Peter's free hand with his own. To Peter, he said, "You get this is a package deal, right?"

"I like the package," Peter said, "so that works out pretty well for me."

—

There was something Tony had not considered when he started dating Peter. Mr. Flopsy had lived years past a rabbit's normal lifespan, but eventually, he'd accrued age markers that even Venom hadn't been able to wipe away—mostly because he refused to step tendril in Mr. Flopsy again following what had happened with Obie. Mr. Flopsy was now in that great pasture in the sky. There was no offloading Venom for a little bit of privacy.

Peter sucked a mark into the side of Tony's neck as he palmed at Tony's ass. "So don't worry about it."

"Venom can't survive in an oxygen rich environment." Tony should be stopping, but instead he was putting his hands up the back of Peter's shirt. "I kind of have to worry about it if you don't want to sleep with him, too."

"You're working from a faulty assumption there," Peter said. He lifted Tony and started walking them toward the bedroom.

"Are you okay with this?" Tony asked Venom.

_We are finally going to mate him,_ Venom said with a mixture of excitement and determination.

"Then I guess I'm on board," Tony said.

Peter suppressed a laugh against Tony's shoulder. "I got that when you kissed me."

—

Peter dropped Tony on the bed and stripped as Tony watched. "You're going to take your clothes off, too, right?"

"Want to see a magic trick?" Tony asked.

"If it's your clothes disappearing, then yes, I do." Peter pulled off his shirt.

_V, that's your cue,_ Tony thought. His clothes disappeared.

Peter paused, hands on his pants. "Okay, that's—I did not actually expect that. That's a pretty cool magic trick."

Tony lay back and enjoyed the show.

"Wait, if that was Venom, does this mean you're always naked?" Peter asked as he got his socks off.

"If I say yes, would you find that sexy or weird?" Tony palmed at his dick as Peter walked up to the bed.

"A bit of both." Peter also put his hand on Tony's dick, which—A+, 10/10, would recommend. Tony groaned as Peter started stroking. Peter kissed Tony and asked, "Do you have condoms somewhere?"

"Um." Fuck. Tony really had not thought this through. "In my defense, I can't get sick, I haven't gotten laid with another human being in over a decade, and Venom takes care of clean-up."

"I don't care if you don't." 

Tony should probably make at least a show of caring. Be the older, more experienced party setting a good example. Instead, he said, "There's a bottle of KY in the bedside drawer."

Peter retrieved it. Tony didn't have a strong opinion on how this should go, but Peter apparently did, because he sat astride Tony's lap and started fingering himself open. Tony put his hands on Peter's hips. 

"You seem very experienced with that," Tony said.

"I am," Peter agreed.

Tony was not a jealous or possessive person. He would like to state that for the record. He was very good at sharing his toys. Look how many precious people he'd given personally designed equipment to (like a brand they willingly wore). It must be Venom who was feeling the urge to fuck Peter so well that he was ruined for anyone else, and Tony was just getting the bleedover.

Peter spread lubricant over Tony with a couple short pulls of his hand, then sank down onto him. He was tight. Tony probably would've spent more time stretching him, which apparently would've been a mistake, because Peter had his eyes closed with a transcendent expression on his face.

"Oh," Peter said. "Oh, wow."

"Good?" Tony asked, holding still and letting Peter set the pace.

"So good," Peter said. The pace he set was slow, lifting up a little, then coming back down again. It was killing Tony, but he was willing to wait.

_You're being lazy,_ Venom chided.

"I'm biding my time," Tony corrected.

"What's Venom saying?" Peter wondered.

"Do you really want to know?" Tony asked.

"I asked, didn't I?" Peter was on his way up when Venom reached a tendril out from Tony's hand to touch Peter's skin. Peter paused.

"You can say no, but if you want, you could also find out firsthand." Tony shouldn't feel this nervous. It wasn't like he was invested in whether Peter wanted to experience a threeway bond to go with the actual threeway happening here. Okay, maybe the jealousy and urge to possess was all him, because _this_ was all Venom.

"He'd come over to me?" Peter asked.

"Not exactly. He'd still be connected to me." Tony ran his hands up and down Peter's sides. "You'd be getting a bit of both of us."

"That's awesome." Peter nodded his head firmly. "Yes, please. I'd love that."

Venom sank into Peter, and Tony switched the majority of his concentration onto what Venom was thinking and feeling for once, getting to experience the sensation like he was doing it himself. Over the years, they'd experimented enough that Tony could use Venom's tendrils like they were extra appendages and could even shove Venom out (which had been necessary a few times for dates Venom had not approved of). For this, though, he was along for the ride, Venom exploring inside Peter's body with a feeling of delight.

_A good fit,_ Venom thought.

"I can hear you." Peter grinned. "Is this what you sound like to Tony?"

Tony took advantage of the connection to send along the thought: _Yes._

Peter's mouth dropped open. "Mr. Stark?"

Tony let a little of his amusement slide over, too, along with wash of heat.

"You—" Peter was a fast study. He got a look of concentration and sent a mishmash of thoughts and emotions. Tony didn't catch most of it, but he got, _Mr. Stark,_ and, _Tony,_ and, _Didn't think it would feel this good._ He got affection and curiosity and joy and love and dismay.

"You didn't get all that, did you?" Peter asked. Concentration had morphed into sheepishness.

Tony sent back affection and admiration and fierce possessiveness and, yes, love, so much love, because he'd move mountains for Peter, would have even before he'd realized he would ever be interested in anything more than friendship and a really odd mentorship in which Peter did his thing and Tony tried and failed to figure out what a mentor even did. Tony had loved Peter long before he'd been in love with him, and that was never going to fade.

"Oh," Peter said softly. He touched a hand to Tony's chest. He looked overwhelmed. He felt hopeful and longing and filled with want. He didn't quite seem to believe it yet.

Tony grabbed Peter's hand and brought his palm to Tony's lips.

_Believe it,_ Tony thought.

Peter's joy warmed Tony the whole way through.

_Told you,_ Venom thought smugly. Then, _You should mate him._

"Yes, Venom, thank you," Tony said, chest shaking with suppressed laughter. "Kind of in the middle of that."

_Keep him,_ Venom said like a clarification.

_Planning on that, too,_ Tony thought, and oh, oops, Peter definitely heard that from the bright spark of feeling that lit up immediately following it.

"You _should_ mate me," Peter said, amusement clear in his expression and his thoughts both.

Tony had done enough biding his time. He flipped them so Peter was under him. "Want to try something new?"

"I hate to break it to you, but this really isn't new for me," Peter said. "I mean, you, yes, and that makes it special, plus the Venom thing, but the rest of this is very familiar."

"Try to reach back," Tony said. He reached through Venom to nestle himself more firmly in Peter's thoughts and feelings, the sensations he was currently experiencing. Peter felt full, on the verge of overwhelmed. There was Tony's dick inside him, but there was also Venom and Tony himself, the unfamiliar input and beginning of a feedback loop. Tony kissed Peter and felt his beard against Peter's skin, pricklier than Tony would have expected. He thrust into Peter slowly, cataloging how it felt at first versus how it felt to change the angle. He experimented with going a little harder, a little faster, and in the process, felt it as Peter figured out how to tap into what Tony was feeling, too. It took hardly any effort to drive Peter right up to the edge. Peter gasped against Tony's mouth, and Tony grinned. "How about now? Still familiar ground?"

"Please," Peter said. _Please, please, please._

Tony pushed Peter over the edge, and Peter pulled Tony with him.

_Are you done?_ Venom wondered as Tony collapsed against Peter.

"Only for the moment," Tony said. "Pretty sure we've got at least a couple rounds in us."

Peter made an unintelligible noise. It felt a lot like, _Maybe three._

"Sure. Let's go for a hat trick." Tony dragged the tip of his nose along Peter's jawline. "Or four. We could do four."

"I can't believe you have that super power, too," Peter said.

"Only with Venom," Tony said.

Peter wasn't protesting. He was already shifting against Tony again in a purposeful way. "You don't have to sell me on a relationship with both of you. I'm already there."

"You are, aren't you?" Tony kept smiling, unable to help himself, overflowing with happiness. He'd never thought he'd get this, someone who was not only willing to put up with Tony's relationship with Venom, but who would embrace it.

Tony had never expected this, but he was so glad to have it.


End file.
